Showing papers by "University of Madras published in 2014"

Visible light degradation of textile effluent using novel catalyst ZnO/γ-Mn2O3

Abstract: The novel ZnO/γ-Mn2O3 (various weight percentages) nanocomposite catalysts were prepared by thermal decomposition method and their size, shape, and surface area were characterized by various techniques. Further, the prepared samples were used to degrade methylene blue (MB) and methyl orange (MO) in aqueous medium under visible light irradiation. Finally, the best catalyst was employed to degrade phenol and a textile effluent. The recycling ability and their efficiency of catalyst are discussed in detail.

Green Synthesized Silver and Gold Nanoparticles for Colorimetric Detection of Hg2+, Pb2+, and Mn2+ in Aqueous Medium

Abstract: In this study, we report a simple and green method for the synthesis of l-tyrosine-stabilized silver (AgNPs) and gold nanoparticles (AuNPs) in aqueous medium under ambient sunlight irradiation. The nanoparticles (NPs) are characterized by UV–visible spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and dynamic light scattering (DLS) techniques. The size and shape of the metal NPs could be controlled by changing the concentration of the substrate, metal precursors, and pH of the medium. The synthesized AgNPs are found to be highly sensitive to Hg2+ and Mn2+ ions with the detection limit for both ions as low as 16 nM under optimized conditions. However AuNPs are found to be sensitive to Hg2+ and Pb2+ ions with a detection limit as low as 53 and 16 nM, respectively. The proposed method was found to be useful for colorimetric detection of heavy metal ions in aqueous medium.

Piper nigrum leaf and stem assisted green synthesis of silver nanoparticles and evaluation of its antibacterial activity against agricultural plant pathogens.

Abstract: Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460 nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7–50 nm and 9–30 nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology.

Role of oxygen vacancy and Fe–O–Fe bond angle in compositional, magnetic, and dielectric relaxation on Eu-substituted BiFeO3 nanoparticles

Abstract: The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol–gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C. The electric relaxation time and activation energy of the oxygen vacancies can be calculated from the Arrhenius equation, and found to be 1.26 eV and 1.76 eV for pure and Eu-substituted BiFeO3, respectively. Substitution induces structural disorder and changes in the Fe–O–Fe bond angle, leading to alteration of the magnetic properties, observed from magnetic studies and evaluated using Rietveld refinement of the XRD patterns. X-ray photoelectron spectroscopy (XPS) confirms the shifting of the binding energy of the Bi 4f orbital, establishing Eu substitution at the Bi site. Calculation of the area under the Fe2+/Fe3+ (2p) and O (1s) XPS spectra gives approximate values of the oxygen vacancies.

Toxicity effect of silver nanoparticles in brine shrimp Artemia.

Abstract: The present study revealed the toxic effect of silver nanoparticles (AgNPs) in Artemia nauplii and evaluated the mortality rate, hatching percentage, and genotoxic effect in Artemia nauplii/cysts. The AgNPs were commercially purchased and characterized using field emission scanning electron microscope with energy dispersive X-ray spectroscopy. Nanoparticles were spherical in nature and with size range of 30–40 nm. Artemia cysts were collected from salt pan, processed, and hatched in sea water. Artemia nauplii (II instar) were treated using silver nanoparticles of various nanomolar concentrations and LC50 value (10 nM) and mortality rate (24 and 48 hours) was evaluated. Hatching percentage of decapsulated cysts treated with AgNPs was examined. Aggregation of AgNPs in the gut region of nauplii was studied using phase contrast microscope and apoptotic cells in nauplii stained with acridine orange were observed using fluorescence microscope. DNA damage of single cell of nauplii was determined by comet assay. This study showed that as the concentration of AgNPs increased, the mortality rate, aggregation in gut region, apoptotic cells, and DNA damage increased in nauplii, whereas the percentage of hatching in Artemia cysts decreased. Thus this study revealed that the nanomolar concentrations of AgNPs have toxic effect on both Artemia nauplii and cysts.

HIV prevention in clinical care settings: 2014 recommendations of the International Antiviral Society-USA Panel.

Abstract: Importance Emerging data warrant the integration of biomedical and behavioral recommendations for human immunodeficiency virus (HIV) prevention in clinical care settings. Objective To provide current recommendations for the prevention of HIV infection in adults and adolescents for integration in clinical care settings. Data Sources, Study Selection, and Data Synthesis Data published or presented as abstracts at scientific conferences (past 17 years) were systematically searched and reviewed by the International Antiviral (formerly AIDS) Society—USA HIV Prevention Recommendations Panel. Panel members supplied additional relevant publications, reviewed available data, and formed recommendations by full-panel consensus. Results Testing for HIV is recommended at least once for all adults and adolescents, with repeated testing for those at increased risk of acquiring HIV. Clinicians should be alert to the possibility of acute HIV infection and promptly pursue diagnostic testing if suspected. At diagnosis of HIV, all individuals should be linked to care for timely initiation of antiretroviral therapy (ART). Support for adherence and retention in care, individualized risk assessment and counseling, assistance with partner notification, and periodic screening for common sexually transmitted infections (STIs) is recommended for HIV-infected individuals as part of care. In HIV-uninfected patients, those persons at high risk of HIV infection should be prioritized for delivery of interventions such as preexposure prophylaxis and individualized counseling on risk reduction. Daily emtricitabine/tenofovir disoproxil fumarate is recommended as preexposure prophylaxis for persons at high risk for HIV based on background incidence or recent diagnosis of incident STIs, use of injection drugs or shared needles, or recent use of nonoccupational postexposure prophylaxis; ongoing use of preexposure prophylaxis should be guided by regular risk assessment. For persons who inject drugs, harm reduction services should be provided (needle and syringe exchange programs, supervised injection, and available medically assisted therapies, including opioid agonists and antagonists); low-threshold detoxification and drug cessation programs should be made available. Postexposure prophylaxis is recommended for all persons who have sustained a mucosal or parenteral exposure to HIV from a known infected source and should be initiated as soon as possible. Conclusions and Relevance Data support the integration of biomedical and behavioral approaches for prevention of HIV infection in clinical care settings. A concerted effort to implement combination strategies for HIV prevention is needed to realize the goal of an AIDS-free generation.

Quercetin reverses EGF-induced epithelial to mesenchymal transition and invasiveness in prostate cancer (PC-3) cell line via EGFR/PI3K/Akt pathway

Abstract: Epidermal growth factor (EGF) plays an important role in metastasis and tumorigenesis of prostate cancer. Epithelial–mesenchymal transition (EMT) is a process in tumor progression during which cancer cells undergo dramatic changes acquiring highly invasive properties. The purpose of this study was to determine the effect of quercetin on EGF-induced EMT in prostate cancer (PC-3) cell line. Quercetin, a plant flavonoid, prevented EGF-induced invasion and migration of PC-3 cells. The protein and mRNA expressions of E-cadherin and N-cadherin were studied by immunocytochemistry, Western blotting and real-time polymerase chain reaction. Quercetin prevented EGF-induced expression of N-cadherin and vimentin and increased the expression of E-cadherin in PC-3 cells, therefore preventing EGF-induced EMT. EGF-induced cell adhesion proteins, intercellular adhesion molecule and vascular cell adhesion molecule were significantly decreased by quercetin treatment. Furthermore, mRNA and protein expressions of Snail, Slug and Twist showed that quercetin significantly decreased EGF-induced expressions of Snail, Slug and Twist. The protein expressions of epidermal growth factor receptor (EGFR)/phosphatidylinositide 3-kinases (PI3K)/Akt/extracellular signal-regulated kinase (ERK)1/2 pathway showed that quercetin prevents EGF-induced EMT via EGFR/PI3k/Akt/ERK1/2 pathway and by suppressing transcriptional repressors Snail, Slug and Twist in PC-3 cells. Thus, it is concluded from the present study that quercetin may prevent cancer metastasis by targeting EMT.

Pyrene Schiff base: photophysics, aggregation induced emission, and antimicrobial properties.

Abstract: Pyrene containing Schiff base molecule, namely 4-[(pyren-1-ylmethylene)amino]phenol (KB-1), was successfully synthesized and well characterized by using 1H, 13C NMR, FT-IR, and EI-MS spectrometry. UV–visible absorption, steady-state fluorescence, time-resolved fluorescence, and transient absorption spectroscopic techniques have been employed to elucidate the photophysical processes of KB-1. It has been demonstrated that the absorption characteristics of KB-1 have been bathochromatically tuned to the visible region by extending the π-conjugation. The extended π-conjugation is evidently confirmed by DFT calculations and reveals that π→π* transition is the major factor responsible for electronic absorption of KB-1. The photophysical property of KB-1 was carefully examined in different organic solvents at different concentrations and the results show that the fluorescence of this molecule is completely quenched due to photoinduced electron transfer. Intriguingly, the fluorescence intensity of KB-1 increases e...

Fabrication of Ni–Fe2O3 magnetic nanorods and application to the detection of uric acid

Abstract: Doping of Ni into Fe2O3 lattices has been achieved by co-precipitation followed by thermal decomposition method. The structural, morphological, and magnetic properties of the fabricated samples were investigated by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FT-IR) spectroscopy, UV-visible absorption (UV-vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results reveal that the Ni is well doped within the lattices of Fe2O3. The Ni dopant suppresses the formation of more stable α-Fe2O3 at higher calcination temperature. Further, the Ni-doped Fe2O3 nanoparticles were used to fabricate an electrochemical sensor (Ni–Fe2O3/GCE) for the detection of uric acid (UA) in biological conditions by cyclic voltammetry (CV) and chronoamperometry (CA). It was found that 5%Ni–Fe2O3/GCE exhibits best response towards UA with less positive potential and larger current response. Furthermore, the sensor gives good linear current response in the concentration range of 6.6 to 112.4 μM with the higher sensitivity of 0.849 μA (μM cm2)−1. Such fabricated sensors are appropriate for newly emerging non-enzymatic electrochemical nanobiosensors.

Identification of Natural Compound Inhibitors for Multidrug Efflux Pumps of Escherichia coli and Pseudomonas aeruginosa Using In Silico High-Throughput Virtual Screening and In Vitro Validation

Abstract: Pseudomonas aeruginosa and Escherichia coli are resistant to wide range of antibiotics rendering the treatment of infections very difficult. A main mechanism attributed to the resistance is the function of efflux pumps. MexAB-OprM and AcrAB-TolC are the tripartite efflux pump assemblies, responsible for multidrug resistance in P. aeruginosa and E. coli respectively. Substrates that are more susceptible for efflux are predicted to have a common pharmacophore feature map. In this study, a new criterion of excluding compounds with efflux substrate-like features was used, thereby refining the selection process and enriching the inhibitor identification process. An in-house database of phytochemicals was created and screened using high-throughput virtual screening against AcrB and MexB proteins and filtered by matching with the common pharmacophore models (AADHR, ADHNR, AAHNR, AADHN, AADNR, AAADN, AAADR, AAANR, AAAHN, AAADD and AAADH) generated using known efflux substrates. Phytochemical hits that matched with any one or more of the efflux substrate models were excluded from the study. Hits that do not have features similar to the efflux substrate models were docked using XP docking against the AcrB and MexB proteins. The best hits of the XP docking were validated by checkerboard synergy assay and ethidium bromide accumulation assay for their efflux inhibition potency. Lanatoside C and diadzein were filtered based on the synergistic potential and validated for their efflux inhibition potency using ethidium bromide accumulation study. These compounds exhibited the ability to increase the accumulation of ethidium bromide inside the bacterial cell as evidenced by these increase in fluorescence in the presence of the compounds. With this good correlation between in silico screening and positive efflux inhibitory activity in vitro, the two compounds, lanatoside C and diadzein could be promising efflux pump inhibitors and effective to use in combination therapy against drug resistant strains of P. aeruginosa and E. coli.

The adoption of a climate disaster resilience index in Chennai, India

Abstract: Results derived from the Climate Disaster Resilience Index (CDRI)-consisting of five dimensions (economic, institutional, natural, physical, and social), 25 parameters, and 125 variables-reflect the abilities of people and institutions to respond to potential climate-related disasters in Chennai, India. The findings of this assessment, applied in the 10 administrative zones of the city, reveal that communities living in the northern and older parts of Chennai have lower overall resilience as compared to the flourishing areas (vis-a-vis economic growth and population) along the urban fringes. The higher resilience of communities along the urban fringes suggests that urbanisation may not necessarily lead to a deterioration of basic urban services, such as electricity, housing, and water. This indication is confirmed by a strong statistical correlation between physical resilience and population growth in Chennai. The identification of the resilience of different urban areas of Chennai has the potential to support future planning decisions on the city's scheduled expansion.

Phthalate exposure in utero causes epigenetic changes and impairs insulin signalling

Abstract: Di-(2-ethylhexyl)phthalate (DEHP) is an endocrine-disrupting chemical (EDC), widely used as a plasticiser. Developmental exposure to EDCs could alter epigenetic programming and result in adult-onset disease. We investigated whether DEHP exposure during development affects glucose homoeostasis in the F1 offspring as a result of impaired insulin signal transduction in gastrocnemius muscle. Pregnant Wistar rats were administered DEHP (0, 1, 10 and 100 mg/kg per day) from embryonic days 9-21 orally. DEHP-exposed offspring exhibited elevated blood glucose, impaired serum insulin, glucose tolerance and insulin tolerance, along with reduced insulin receptor, glucose uptake and oxidation in the muscle at postnatal day 60. The levels of insulin signalling molecules and their phosphorylation were down-regulated in DEHP-exposed offspring. However, phosphorylated IRS1(Ser636/639), which impedes binding of downstream effectors and the negative regulator (PTEN) of PIP3, was increased in DEHP-exposed groups. Down-regulation of glucose transporter 4 (Glut4 (Slc2a4)) gene expression and increased GLUT4(Ser488) phosphorylation, which decreases its intrinsic activity and translocation towards the plasma membrane, were recorded. Chromatin immunoprecipitation assays detected decreased MYOD binding and increased histone deacetylase 2 interaction towards Glut4, indicative of the tight chromatin structure at the Glut4 promoter. Increased DNMTs and global DNA methylation levels were also observed. Furthermore, methylation of Glut4 at the MYOD-binding site was increased in DEHP-exposed groups. These findings indicate that, gestational DEHP exposure predisposes F1 offspring to glucometabolic dysfunction at adulthood by down-regulating the expression of critical genes involved in the insulin signalling pathway. Furthermore, DEHP-induced epigenetic alterations in Glut4 appear to play a significant role in disposition towards this metabolic abnormality.

Zeolite encapsulated Ni(II) and Cu(II) complexes with tetradentate N2O2 Schiff base ligand: catalytic activity towards oxidation of benzhydrol and degradation of rhodamine-B

Abstract: Nickel(II) and copper(II) complexes of the Schiff base ligand O,O′-trimethyl bis (salicylidene isonicotinylhydrazone) (H2L) were synthesized and characterized. The encapsulation of these complexes in the cavities of the zeolite was achieved by a fixed ligand method (FLM). The free complexes (FC) and the retention of the zeolite encapsulated metal complexes [ZEMC; i.e., Ni(II)L–Y, Cu(II)L–Y] were investigated by several spectroscopic, thermal analysis, sorption and microscopic techniques [i.e., FTIR, NMR, ESI-mass, conductivity, DRS/UV-Vis, EPR, XPS, AAS, TGA, XRD, nitrogen isotherm, magnetic and (SEM/TEM)EDX]. This study reveals the formation and stability of the metal complexes in the cavities of the zeolite. The catalytic activities of free complexes and encapsulated complexes were studied in the liquid phase oxidation of benzhydrol/H2O2 and the photodegradation of rhodamine-B (RhB) under UV/visible (H2O2) irradiation. The catalytic activities of benzhydrol (BH) oxidation and RhB degradation were higher with free complexes and encapsulated complexes, respectively. In most cases, the copper(II) [Cu(II)L·2ClO4, Cu(II)L–Y] complexes showed better activity than the nickel(II) complexes [Ni(II)L·2ClO4, Ni(II)L–Y] in both BH and RhB degradation reactions. The enhancement of Cu(II)L–Y activity was mainly due to the metal present in the cavities and on the surface. Hence, in the case of FC, rate of the reaction (% of conversion) for the copper(II) complexes is more than that for nickel(II) in BH oxidation, but, in the case of ZEMC, the photocatalytic activity and rate of reaction (% of conversion) were more for Cu(II)L–Y than Ni(II)L–Y. These results show that both the oxidation reactions follow pseudo first order kinetics. The catalytic activities of the recovered and purified ZEMC were compared with the fresh catalyst.

Nanostructured Bi(1−x)Gd(x)FeO3 – a multiferroic photocatalyst on its sunlight driven photocatalytic activity

Abstract: The photocatalytic activity of sol–gel synthesized nanostructured Bi1−xGdxFeO3 (x = 0, 0.05, 0.1, 0.15) particles on the degradation of methylene blue (MB) was demonstrated for the first time under sunlight. The X-ray diffraction (XRD) studies showed that the substitution induced structural changes in 10 and 15% Gd substituted BiFeO3 (BFO). The morphology analysis, by field emission scanning (FESEM) and high resolution transmission electron microscopy (HRTEM), presented the composition driven particle size reduction and morphology changes in BFO from irregular to spherical shape. The band gap estimation by UV-visible diffuse reflectance spectroscopy revealed that increasing concentration of Gd significantly reduced the band gap of BFO from 2.38 eV to 2.29 eV. An anomalous magnetic enhancement was observed in Bi0.90Gd0.10FeO3 nanoparticles due to the manifestation of antiferromagnetic (AFM) core–ferromagnetic (FM) shell-like structure, revealed by its M–H hysteresis curve. An increasing trend in the photocatalytic activity of BFO was observed with increasing concentration of Gd. In this case, enhanced photocatalytic activity observed in Bi0.85Gd0.15FeO3 could be due to its increased ferroelectric domains that drive the charge carriers to the catalyst surface–dye interface, leading to more effective degradation of the dye. Conversely, an anomalous photocatalytic activity was observed in Bi0.90Gd0.10FeO3 that should be attributed to its AFM–FM core–shell-like structure.

Biochemical responses and mitochondrial mediated activation of apoptosis on long-term effect of aspartame in rat brain

Abstract: Aspartame, an artificial sweetener, is very widely used in many foods and beverages. But there are controversies about its metabolite which is marked for its toxicity. Hence it is believed to be unsafe for human use. Previous studies have reported on methanol exposure with involvements of free radicals on excitotoxicity of neuronal apoptosis. Hence, this present study is proposed to investigate whether or not chronic aspartame (FDA approved Daily Acceptable Intake (ADI),40 mg/kg bwt) administration could release methanol, and whether or not it can induce changes in brain oxidative stress status and gene and protein expression of anti-apoptotic Bcl-2 and pro-apoptotic Bax and caspase-3 in the rat brain region. To mimic the human methanol metabolism, Methotrexate (MTX)-treated Wistar strain male albino rats were used and after the oral administration of aspartame, the effects were studied along with controls and MTX-treated controls. Aspartame exposure resulted with a significant increase in the enzymatic activity in protein carbonyl, lipid peroxidation levels, superoxide dismutase, glutathione-S-transferase, glutathione peroxidase and catalase activity in (aspartame MTX)-treated animals and with a significant decrease in reduced glutathione, glutathione reductase and protein thiol, pointing out the generation of free radicals. The gene and protein expression of pro apoptotic marker Bax showed a marked increase whereas the anti-apoptotic marker Bcl-2 decreased markedly indicating the aspartame is harmful at cellular level. It is clear that long term aspartame exposure could alter the brain antioxidant status, and can induce apoptotic changes in brain.

New electrochemical sensor based on Ni-doped V2O5 nanoplates modified glassy carbon electrode for selective determination of dopamine at nanomolar level

Abstract: Ni-doped (0, 2, 5 and 7 wt%)V2O5 nanoparticles were prepared by thermal decomposition method. The as-prepared nanoparticles are characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, UV–Vis absorption spectroscopy, scanning electron microscopy (SEM) and high resolution-transmission electron microscopy (HR-TEM). The results indicated that the Ni2+ ions are well doped within V2O5 lattices. Compared with pure V2O5, Ni-doped V2O5 (Ni-V2O5) nanoparticles exhibit enhanced dopamine (DA) sensing property. Particularly, 7%Ni-V2O5 nanoplates modified glassy carbon electrode (7%Ni-V2O5/GCE) showed a good response to the DA concentration in the range of 6.6–96.4 μM with sensitivity of 132 nA μM−1. The obtained limit of detection (LOD) is 28 nM (S/N = 3). A possible mechanism related to the electrochemical oxidation of DA was proposed. Further, the proposed method was successfully utilized to determine DA in dopamine hydrochloride solution (11–13 μM) and reasonable results were obtained. The results showed that the 7%Ni-V2O5/GCE exhibits an excellent electrocatalytic activity, good sensitivity, reproducibility, repeatability and long-term stability.

High Level Aminoglycoside Resistance and Distribution of Aminoglycoside Resistant Genes among Clinical Isolates of Enterococcus Species in Chennai, India

Abstract: Enterococci are nosocomial pathogen with multiple-drug resistance by intrinsic and extrinsic mechanisms. Aminoglycosides along with cell wall inhibitors are given clinically for treating enterococcal infections. 178 enterococcal isolates were analyzed in this study. E. faecalis is identified to be the predominant Enterococcus species, along with E. faecium, E. avium, E. hirae, E. durans, E. dispar and E. gallinarum. High level aminoglycoside resistance (HLAR) by MIC for gentamicin (GM), streptomycin (SM) and both (GM + SM) antibiotics was found to be 42.7%, 29.8%, and 21.9%, respectively. Detection of aminoglycoside modifying enzyme encoding genes (AME) in enterococci was identified by multiplex PCR for aac(6')-Ie-aph(2'')-Ia; aph(2'')-Ib; aph(2'')-Ic; aph(2'')-Id and aph(3')-IIIa genes. 38.2% isolates carried aac(6')-Ie-aph(2'')-Ia gene and 40.4% isolates carried aph(3')-IIIa gene. aph(2'')-Ib; aph(2'')-Ic; aph(2'')-Id were not detected among our study isolates. aac(6')-Ie-aph(2'')-Ia and aph(3')-IIIa genes were also observed in HLAR E. durans, E. avium, E. hirae, and E. gallinarum isolates. This indicates that high level aminoglycoside resistance genes are widely disseminated among isolates of enterococci from Chennai.